Building Social into Solr

We have had a number of customers inquire about customizing specific aspects of Solr search with Jumper.

There are really two approaches: one is to build Jumper tagging into your search engine interface allowing users to tag documents or content when it is stored. The second is to import Jumper tagging fields into solr using the DataImportHandler. This is done using basic JDBC connectivity. Tags stored in the Jumper search engine then are imported into the Solr index and attached to a document and returned when searched. Using faceted_fields you can allow users to filter search based on the knowledge tags applied by other users.

This is perhaps the easiest method. The two services can be bundled in a single web interface. In this way you are removing the Jumper search engine and replacing it with Solr. This gives you the benefit of both worlds – full text searching and user tagging – to deliver better more detailed search results.

If you prefer to embed custom search paths into Solr the primary method is using facet-fields. A Jumper tagging interface can be added when storing documents. The Jumper tag fields are then stored as facet_fields that Solr will search in addition to its full text parsing of the document. This is done on indexed rather than stored values.

This requires that we add a number of Jumper tags to the Solr index separately and add a custom sort to Solr search. Adding a new Jumper tag field to the search results requires two very small hook implementations: hook_apachesolr_update_index() and hook_apachesolr_modify_query(). To start, let’s just add the keyword tag field to the Solr index.

/**
* Implementation of hook_apachesolr_update_index()
*/
function mymodule_apachesolr_update_index(&$document, $node) {
// Index field_keyword_tag as a separate field
if ($node->type == 'profile') {
$user = user_load(array('uid' => $node->uid));
$document->setMultiValue('sm_field_keyword_tag', $user->tags);
}
elseif (count($node->field_keyword_tag)) {
foreach ($node->field_keyword_tag AS $keyword) {
$document->setMultiValue('sm_field_keyword_tag', $keyword['filepath']);
}
}
}

All we do is add the data to the index by adding it to the $document object, which is passed by reference. We used the setMultiValue method since the tag field can have multiple values, but if we were just adding one field, we would just use the addField method. The field name is simply the 'sm_' dynamic field name pattern with field_keyword_tag appended, since the field contains a keyword string, and the sm_ field type represents a small string.

Now that the data has been added to the index, we also need to add it to the query so it can be returned with the search results:
function mymodule_apachesolr_modify_query(&$query, &$params, $caller) {
$params['fl'] .= ',sm_field_keyword_tag';
}

And that's all there is to it… This can be repeated for each of the Jumper knowledge tags that you want to add. All you're doing is some basic PHP string concatenation and appending your newly indexed field to the fields to return array (['fl'])of the $params object. Although, we are simplifying the detail a little bit on the format of $params for the sake of brevity in this post.

In general, adding Jumper social tagging features into your Solr search is pretty easy, and can deliver some very powerful capabilities to your search functionality.